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Jul 17, 2015
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Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Troubleshooting with MySQL Performance Schema Ivan Ma 2015-01-10
Join Hong Kong MySQL User Group on Facebook
Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Safe Harbor Statement
The following is intended to outline our general product direction. It is intended for information purposes only, and may not be incorporated into any contract. It is not a commitment to deliver any material, code, or functionality, and should not be relied upon in making purchasing decisions. The development, release, and timing of any features or functionality described for Oracle’s products remains at the sole discretion of Oracle.
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MySQL : Agenda
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Why and What – Performance Schema
Performance Schema Tables
Using MySQL Workbench
Try and See !
Questions
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Why Performance Schema?
System Low throughput?
?
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DBA
Hot table?
Network
High traffic on link?
Storage
Too much disk spin? App Developer
Slow application?
MySQL Developer
Code contention?
End User
Stuck session?
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What is Performance Schema
• The MySQL Performance Schema is a feature for monitoring MySQL Server execution at a low level.
– to inspect internal execution of the server at runtime. (Data Collection by Instrumentation at code level. No separate threads.)
– implemented using the PERFORMANCE_SCHEMA storage engine
– to monitor server events. An “event” is anything the server does that takes time and has been instrumented so that timing information can be collected.
• Tables in the performance_schema database are views or temporary tables that use no persistent on-disk storage.
• No memory allocation is done beyond that which occurs during server startup
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The Journey : Then and now..
• MySQL 5.5 (1st Release P_S)
• Only waits events
– Mutex waits
– Conditions waits
– R/W locks waits
– File I/O waits
• Setup_(timers/consumers/instruments) tables
• Few summary tables
• 17 Tables and 218 Instruments
• MySQL 5.6
• Statements and stages
• Table, Index and network I/O. Table locks
• Host Cache
• User, account, host
• Setup_(actor/objects)
• Multiple summary tables
• Events’ hierarchy
• 52 Tables and 550 Instruments
• MySQL 5.7 (DMRs)
• Instrumentation:
– Transactions
– Metadata locks
– Prepared statements
– Stored programs
– Memory usage
• User variables
• Replication summary tables
• 76 Tables and 885 Instruments
• … 6
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MySQL performance_schema Database
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MySQL 5.6 Performance Schema Tables
• setup_% tables
• event_% tables
– Category • stage
• statement
• wait
– Type • current
• history
• Summary Tables
• Instances tables
• Connection tables
• Misc Tables
– host cache table
– performance timers
– threads
– users
– session*attrs
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Some notes with Using MySQL Workbench
• Default SQL Editor with MySQL Workbench is using ‘Safe update mode’
– Edit Perference
• Why care –
– With Performance Schema, No KEY
– Update setup_% tables may not have ‘key’ on where clause
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Performance Schema Options …(1)
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Performance Schema Options …(2)
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Performance Schema Options …(3)
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Default P_S setup_consumer
• Only a few instrumentation is ON
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setup_actor
• (HOST, USER, ROLE) default with (‘%’, ‘%’, ’%’)
• All foreground threads are monitored.
• Update to this table has no change to existing started threads.
• Demo
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Summary Tables
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Getting statements summary by account (e.g. ‘tpcc’)
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Why the SQL takes so long to run …
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At this moments
• We see
– How we can enable Performance Schema
– What to see (enable what you want to see to reduce the overhead) • e.g. Only the session with the user login
– Statement taking too long to run
• What about “Wait Time”, “IO Time”, “Thread”, “Internal Stages”
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A Better way to look at this by using sys schema
• Using MySQL Workbench
– The first time clicking the Performance Schema Setup Install SYS schema
• SYS Schema
– A set of VIEWs on the Performance Schema
– A set of SPs to make things easier • to clean up performance schema tables
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Summary
• Using Performance Schema
– Data Collection
– As a tools
– Overhead! Enable what you want to see.
• Using SYS Schema
– Friendly VIEWs to explore performance data set
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